While working on an desktop AIR application, I came across the problem that the copyToAsync method of the flash.filesystem.File class does not fire a ProgressEvent.
I would love to use the Async method, because this does not hold up the rest of the application, but I wanted to display some progress indication in e.g. a ProgressBar.
Solution:
Open 2 streams, one to read from and one to write to. Read and write chunks of bytes and calculate the progress according to the bytesAvailable attribute of the read stream.
Sample code:
// This is an object which has a public attribute which contains the source of the file to copy and
// a public function with a File parameter to copy it to
public var fileObject:File;
public function copyTo(destination:File):void {
inStream = new FileStream();
outStream = new FileStream();
inStream.addEventListener(ProgressEvent.PROGRESS, onProgress );
inStream.addEventListener(Event.COMPLETE, onReady );
inStream.openAsync(fileObject, FileMode.READ);
outStream.openAsync(destination, FileMode.WRITE);
}
private function onProgress(e:ProgressEvent):void {
// calculate the percentage
pct = Math.round(e.bytesLoaded/e.bytesTotal*100);
// if you want to update the progress bar:
bar.setProgress(pct, 100);
// if the ProgressEvent is fired, we have data available in the inStream, so we can start writing data
var bytes:ByteArray = new ByteArray();inStream.readBytes(bytes, 0, inStream.bytesAvailable);
outStream.writeBytes(bytes, 0, bytes.length);
}
private function onReady(e:Event):void {
// the whole stream is read, so close the files
inStream.close();
outStream.close();
// dispatch a COMPLETE event to let listeners to this object know the copy is done
fileObject.dispatchEvent(new Event(Event.COMPLETE));
}
And somewhere in the application, associated with the copying process, there's a progress bar like this:
<mx:progressbar id="bar" mode="manual" width="100%"/>
I'm sorry this code's not entirely complete, but I had to use fragments of my existing code to illustrate this principle. Feel free to experiment with it.
